It all depends on what you want to do.
If you enjoy working with networks, go for a CCNA. If you like working on Windows servers, go for a MCSE. If you like working with Linux and specifically Red Hat, go for RHCE.
first of all it depends on your area of interest also as said above. you want to live more into servers then MS. routers and switches etc. Cisco. RH is entirely a different stream.
scope wise MS has higher probability of better prospects. then Cisco and last will be Linux